There is an increasing trend toward the use of expanded synthetic resins for manufacturing miscellaneous bodies such as packages, structures and wall elements, containers, or various receptacles. Most of these bodies have an irregular outer surface which cannot be written on or otherwise carry legible inscriptions concerning the product enclosed therein, its destination, or its manufacturer. At the same time such containers are so soft that the handling incident to shipping often scratches them up so badly that they are quite unattractive, if they have not opened by themselves.
Packages consisting essentially of shells or half-casings of expanding synthetic resin, e.g. foamed urethane, are already know and widely used. Due to their poor mechanical strength these shells or half-casings are not used as widely as could be desired. Each shell or the like may contain several objects in different respective cavities or cutouts, but can only be used for packing objects having a well-defined shape. If this shape is modified a new package must be prepared. This limits considerably the use of such packages since a great many different types must be kept on hand and they must also be shipped in their own cartons so that they may be marked and so that the soft foam will not be ruined.
A known packing method consists in utilizing polyurethane as a filler between the objects to be protected and a fluid-tight case. The objects are enclosed in a fluid-tight envelope from which the air is removed as much as possible by an expensive vacuum pump. Then the bagged object is placed in the case on blocks or wedges, the interior of the case being lined with some kind of sheet material acting as a mold-release agent. The reagent mixture is then introduced slowly into the case in order to fill it completely and prevent the formation of air pockets or bubbles. A lid is then nailed in place and the entire mass is allowed to cure.
Although such a package is generally considered to be very good, it has certain disadvantages. The blocks or wedges supporting the object on the bottom of the case transmit shocks due to handling directly to the object. In addition opening such a package is quite difficult since chunks of the packaging foam must be cut away, which is quite dangerous the closer the unpackager gets to the object.